Bitcoin blew past $9,700 just a week after topping $8,000 and approached its closest ever to five figures, gaining mainstream market attention as it defies bubble warnings.

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Hedge fund manager Mike Novogratz, who is starting a $500 million fund to invest in cryptocurrencies, said last week that bitcoin would end the year at $10,000. A day later, Fundstrat head of research Thomas Lee doubled his price target to $11,500 by the middle of 2018.

In a move toward mainstream investing, CME Group Inc. has said it plans to start offering futures contracts for bitcoin, which could begin trading in December. JPMorgan Chase & Co., the largest U.S. bank, was weighing last week whether to help clients bet on bitcoin via the proposed futures contracts, according to a person with knowledge of the situation.